Synthesis of Fine Nickel Powders by Solvothermal Method

Abstract:

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Fine nickel powders have been prepared by chemical reduction between nickel acetate and
alcohol under solvothermal conditions. The effect of adding surfactant and varying solvent on the
particle size of the as-synthesized nickel powders have been explored. SEM, XRD and TG were
employed to characterize the size, morphology, crystalline structure and the thermal stability of the
as-synthesized nickel powders. It is revealed that the FCC-structured nickel powders are of uniform
spherical shape with good crystallinity and thermal stability. Typically, nickel powders with an
average size of 300 nm were obtained at 200°C for 8 h using 0.04 mol/L solution of
Ni(CH3COO)2·4H2O in n-butyl alcohol under solvothermal conditions.

Abstract: Nickel nanoparticles were prepared by reduction of nickel-hydrazine complex with sodium
borohydride (NaBH4) in water-in-oil (w/o) microemulsion of PVP/ethanol/toluene/water at 50C. It
was investigated through SEM and TEM photographs that the nickel nanoparticles with a diameter
15~20nm were nearly monodispersed. By the analysis of XRD, the resulting particles were
characterized to be pure crystalline nickel with a face-centered cubic structure. The results indicate
that the size, shape and distribution of particles depend on the mole ratio of [water]/[PVP] and
[NaBH4]/[Ni]. Also, it was found that particle size could be controlled by the kinds of surfactants.

Abstract: The high energy ball milling of Ni-50 atom % Si elemental powder mixtures was carried
out using a planetary mill. X-ray diffraction (XRD) was used to identify the phase evolutions during
the high energy ball milling period. The microstructure morphology of the powders milled different
time was determined by field emission scanning electron microscope (FESEM). The beginning time
of mechanical alloying was determined by back scattered electrons (BSE) images. The XRD
patterns showed that the nickel peaks intensity and the silicon peaks intensity obviously decreased
with milling time increased to 1 hour. BSE images revealed that nickel and silicon powders were
not blended uniformly for 1 hour of milling. It was found that NiSi formed as the milling time
increased to 5 hours, simultaneously, the nickel peaks and the silicon peaks almost disappeared.
That means the obvious mechanical alloying started from 5 hours of milling. BSE images agreed
with the result analyzed from XRD patterns. With the milling time further increased from 10 to 75
hours, the NiSi peaks decreased gradually, at the same time, the Ni2Si peaks appeared and then
increased gradually.

Abstract: Nano-sized nickel powders were prepared through a wet chemical reduction, of NiCl2 by sodium in liquid ammonia at -45 °C, and a subsequent heat-treatment in vacuum at 300 °C. The prepared product was systematically characterized by X-ray diffraction (XRD), scan electron microscopy (SEM), transmission electron microscopy (TEM), and BET specific surface area measurement. The results show that the product was composed of nano-sized nickel particles, with average particle diameter of about 20 nm, and specific surface area of about 30 m2g-1. The possible formation mechanism of the nano-sized nickel powder was also discussed briefly.